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What is the Casimir Effect?

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What is the Casimir Effect?

Illustration of the Casimir effect.

Emok, via Wikimedia Commons: http://en.wikipedia.org/wiki/File:Casimir_plates.svg
Question: What is the Casimir Effect?
Answer:

The Casimir Effect is a result of quantum physics that seems to defy the logic of the everyday world. In this case, it results in energy from "empty space" actually exerting a force on physical objects. While this may seem bizarre, the fact of the matter is that the Casimir Effect has been experimentally verified many times over and provides some useful applications in some areas of nanotechnology.

How the Casimir Effect Works

The most basic description of the Casimir Effect includes a situation where you have two uncharged metallic plates near each other, with a vacuum between them. We normally think that there's nothing between the plates (and therefore no force), but it turns out that when the situation is analyzed using quantum electrodynamics, something unexpected happens. The virtual particles created within the vacuum create virtual photons which interact with the uncharged metal plates. As a result, if the plates are extremely close together (less than a micron) then this will become the dominant force. The force drops off quickly the further apart the place is. Still, this effect has been measured to within about 15% of the value predicted by the theory itself, making it clear that the Casimir effect is quite real.

History and Discovery of the Casimir Effect

Two Dutch physicists working at the Philips Research Lab in 1948, Hendrik B. G. Casimir and Dirk Polder, suggested the effect while working on fluid properties, such as why mayonnaise flows so slowly ... which just goes to show that you never know where a major insight will come from.

Dynamic Casimir Effect

A variant of the Casimir Effect is the dynamic Casimir effect. In this case, one of the plates moves and causes the accumulation of photons within the region between the plates. These plates are mirrored, so that the photons continue to accumulate between them. This effect was experimentally verified in May 2011 (as reported in Scientific American and Technology Review). It is demonstrated (without much fanfare ... or audio) on this YouTube video.

Potential Applications

One potential application would be to apply the dynamic Casimir effect as a means of creating a propulsion engine for a spacecraft, which would theoretically propel the ship by using the energy from the vacuum. This is a highly ambitious application of the effect, but it appears to be one suggested to a bit of fanfare by an Egyptian teenager, Aisha Mustafa, who has patented the invention. (This alone doesn't mean much, of course, since there's even a patent on a time machine, as described in Dr. Ronald Mallett's non-fiction book Time Traveler. A lot of work must still be done to see if this is feasible or if it is just another fancy and failed attempt at a perpetual motion machine, but here are a handful of articles focusing on the initial announcement (and I'll add more as I hear about any progress):

There have also been various suggestions that the bizarre behavior of the Casimir effect could have applications in nanotechnology - that is, in very small devices built at atomic sizes.

Another suggestion put forth has been tiny "Casimir oscillators" which would be a tiny oscillator that could be used in various nanomechanical systems. This particular hypothetical application is explained in greater and more technical detail in the 1995 Journal of Microelectromechanical Systems article "The Anharmonic Casimir Oscillator (ACO)-- The Casimir Effect in a Model Microelectromechanical System."

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